PARIS, April 8 (Reuters) - NATO's secretary-general warned Russia on Tuesday that if it were to encroach into eastern Ukraine there would be "grave consequences" for its relationship with the allaince.

"If Russia were to intervene further in Ukraine it would be a historic mistake," Anders Fogh Rasmussen told a news conference in Paris.

"It would have grave consequences for our relationship with Russia and would further isolate Russia inetrnationally." (Reporting By John Irish; editing by Mark John)